Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0
2 : /*
3 : * fs/ioprio.c
4 : *
5 : * Copyright (C) 2004 Jens Axboe <axboe@kernel.dk>
6 : *
7 : * Helper functions for setting/querying io priorities of processes. The
8 : * system calls closely mimmick getpriority/setpriority, see the man page for
9 : * those. The prio argument is a composite of prio class and prio data, where
10 : * the data argument has meaning within that class. The standard scheduling
11 : * classes have 8 distinct prio levels, with 0 being the highest prio and 7
12 : * being the lowest.
13 : *
14 : * IOW, setting BE scheduling class with prio 2 is done ala:
15 : *
16 : * unsigned int prio = (IOPRIO_CLASS_BE << IOPRIO_CLASS_SHIFT) | 2;
17 : *
18 : * ioprio_set(PRIO_PROCESS, pid, prio);
19 : *
20 : * See also Documentation/block/ioprio.rst
21 : *
22 : */
23 : #include <linux/gfp.h>
24 : #include <linux/kernel.h>
25 : #include <linux/ioprio.h>
26 : #include <linux/cred.h>
27 : #include <linux/blkdev.h>
28 : #include <linux/capability.h>
29 : #include <linux/syscalls.h>
30 : #include <linux/security.h>
31 : #include <linux/pid_namespace.h>
32 :
33 0 : int ioprio_check_cap(int ioprio)
34 : {
35 0 : int class = IOPRIO_PRIO_CLASS(ioprio);
36 0 : int data = IOPRIO_PRIO_DATA(ioprio);
37 :
38 0 : switch (class) {
39 : case IOPRIO_CLASS_RT:
40 : /*
41 : * Originally this only checked for CAP_SYS_ADMIN,
42 : * which was implicitly allowed for pid 0 by security
43 : * modules such as SELinux. Make sure we check
44 : * CAP_SYS_ADMIN first to avoid a denial/avc for
45 : * possibly missing CAP_SYS_NICE permission.
46 : */
47 0 : if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_NICE))
48 : return -EPERM;
49 : fallthrough;
50 : /* rt has prio field too */
51 : case IOPRIO_CLASS_BE:
52 0 : if (data >= IOPRIO_NR_LEVELS || data < 0)
53 : return -EINVAL;
54 : break;
55 : case IOPRIO_CLASS_IDLE:
56 : break;
57 : case IOPRIO_CLASS_NONE:
58 0 : if (data)
59 : return -EINVAL;
60 : break;
61 : default:
62 : return -EINVAL;
63 : }
64 :
65 : return 0;
66 : }
67 :
68 0 : SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
69 : {
70 : struct task_struct *p, *g;
71 : struct user_struct *user;
72 : struct pid *pgrp;
73 : kuid_t uid;
74 : int ret;
75 :
76 0 : ret = ioprio_check_cap(ioprio);
77 0 : if (ret)
78 0 : return ret;
79 :
80 0 : ret = -ESRCH;
81 : rcu_read_lock();
82 0 : switch (which) {
83 : case IOPRIO_WHO_PROCESS:
84 0 : if (!who)
85 0 : p = current;
86 : else
87 0 : p = find_task_by_vpid(who);
88 0 : if (p)
89 0 : ret = set_task_ioprio(p, ioprio);
90 : break;
91 : case IOPRIO_WHO_PGRP:
92 0 : if (!who)
93 0 : pgrp = task_pgrp(current);
94 : else
95 0 : pgrp = find_vpid(who);
96 :
97 0 : read_lock(&tasklist_lock);
98 0 : do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
99 0 : ret = set_task_ioprio(p, ioprio);
100 0 : if (ret) {
101 0 : read_unlock(&tasklist_lock);
102 0 : goto out;
103 : }
104 0 : } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
105 0 : read_unlock(&tasklist_lock);
106 :
107 0 : break;
108 : case IOPRIO_WHO_USER:
109 0 : uid = make_kuid(current_user_ns(), who);
110 0 : if (!uid_valid(uid))
111 : break;
112 0 : if (!who)
113 0 : user = current_user();
114 : else
115 0 : user = find_user(uid);
116 :
117 0 : if (!user)
118 : break;
119 :
120 0 : for_each_process_thread(g, p) {
121 0 : if (!uid_eq(task_uid(p), uid) ||
122 0 : !task_pid_vnr(p))
123 0 : continue;
124 0 : ret = set_task_ioprio(p, ioprio);
125 0 : if (ret)
126 : goto free_uid;
127 : }
128 : free_uid:
129 0 : if (who)
130 0 : free_uid(user);
131 : break;
132 : default:
133 : ret = -EINVAL;
134 : }
135 :
136 : out:
137 : rcu_read_unlock();
138 0 : return ret;
139 : }
140 :
141 : /*
142 : * If the task has set an I/O priority, use that. Otherwise, return
143 : * the default I/O priority.
144 : *
145 : * Expected to be called for current task or with task_lock() held to keep
146 : * io_context stable.
147 : */
148 0 : int __get_task_ioprio(struct task_struct *p)
149 : {
150 0 : struct io_context *ioc = p->io_context;
151 : int prio;
152 :
153 0 : if (p != current)
154 : lockdep_assert_held(&p->alloc_lock);
155 0 : if (ioc)
156 0 : prio = ioc->ioprio;
157 : else
158 : prio = IOPRIO_DEFAULT;
159 :
160 0 : if (IOPRIO_PRIO_CLASS(prio) == IOPRIO_CLASS_NONE)
161 0 : prio = IOPRIO_PRIO_VALUE(task_nice_ioclass(p),
162 : task_nice_ioprio(p));
163 0 : return prio;
164 : }
165 : EXPORT_SYMBOL_GPL(__get_task_ioprio);
166 :
167 : static int get_task_ioprio(struct task_struct *p)
168 : {
169 : int ret;
170 :
171 0 : ret = security_task_getioprio(p);
172 : if (ret)
173 : goto out;
174 0 : task_lock(p);
175 0 : ret = __get_task_ioprio(p);
176 0 : task_unlock(p);
177 : out:
178 : return ret;
179 : }
180 :
181 : /*
182 : * Return raw IO priority value as set by userspace. We use this for
183 : * ioprio_get(pid, IOPRIO_WHO_PROCESS) so that we keep historical behavior and
184 : * also so that userspace can distinguish unset IO priority (which just gets
185 : * overriden based on task's nice value) from IO priority set to some value.
186 : */
187 : static int get_task_raw_ioprio(struct task_struct *p)
188 : {
189 : int ret;
190 :
191 0 : ret = security_task_getioprio(p);
192 : if (ret)
193 : goto out;
194 0 : task_lock(p);
195 0 : if (p->io_context)
196 0 : ret = p->io_context->ioprio;
197 : else
198 : ret = IOPRIO_DEFAULT;
199 0 : task_unlock(p);
200 : out:
201 : return ret;
202 : }
203 :
204 : static int ioprio_best(unsigned short aprio, unsigned short bprio)
205 : {
206 0 : return min(aprio, bprio);
207 : }
208 :
209 0 : SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
210 : {
211 : struct task_struct *g, *p;
212 : struct user_struct *user;
213 : struct pid *pgrp;
214 : kuid_t uid;
215 0 : int ret = -ESRCH;
216 : int tmpio;
217 :
218 : rcu_read_lock();
219 0 : switch (which) {
220 : case IOPRIO_WHO_PROCESS:
221 0 : if (!who)
222 0 : p = current;
223 : else
224 0 : p = find_task_by_vpid(who);
225 0 : if (p)
226 0 : ret = get_task_raw_ioprio(p);
227 : break;
228 : case IOPRIO_WHO_PGRP:
229 0 : if (!who)
230 0 : pgrp = task_pgrp(current);
231 : else
232 0 : pgrp = find_vpid(who);
233 0 : read_lock(&tasklist_lock);
234 0 : do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
235 0 : tmpio = get_task_ioprio(p);
236 0 : if (tmpio < 0)
237 0 : continue;
238 0 : if (ret == -ESRCH)
239 : ret = tmpio;
240 : else
241 0 : ret = ioprio_best(ret, tmpio);
242 0 : } while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
243 0 : read_unlock(&tasklist_lock);
244 :
245 0 : break;
246 : case IOPRIO_WHO_USER:
247 0 : uid = make_kuid(current_user_ns(), who);
248 0 : if (!who)
249 0 : user = current_user();
250 : else
251 0 : user = find_user(uid);
252 :
253 0 : if (!user)
254 : break;
255 :
256 0 : for_each_process_thread(g, p) {
257 0 : if (!uid_eq(task_uid(p), user->uid) ||
258 0 : !task_pid_vnr(p))
259 0 : continue;
260 0 : tmpio = get_task_ioprio(p);
261 0 : if (tmpio < 0)
262 0 : continue;
263 0 : if (ret == -ESRCH)
264 : ret = tmpio;
265 : else
266 0 : ret = ioprio_best(ret, tmpio);
267 : }
268 :
269 0 : if (who)
270 0 : free_uid(user);
271 : break;
272 : default:
273 : ret = -EINVAL;
274 : }
275 :
276 : rcu_read_unlock();
277 0 : return ret;
278 : }
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